The raid on Boulogne in 1801 was a failed attempt by elements of the Royal Navy led by Vice Admiral Lord Horatio Nelson to destroy a flotilla of French vessels anchored in the port of Boulogne, a fleet which was thought to be used for the invasion of England, during the French Revolutionary Wars. At dawn on 4 August, Nelson ordered five bomb vessels to move forward and open fire against the French line. Despite the inferior gunpowder of French artillery and the high number of shots fired by the bomb vessels, the British sustained more casualties and withdrew. The night of 16 August Nelson returned and tried to bring off the flotilla, attacking with seventy boats and nearly two thousand men organized into four divisions, but the attack was successfully repelled by the defenders, led by Admi